Karma makes a social gifting app that lets recipients choose whether to receive a tchotchke or donate the cost of whatever they were going to get to charity instead.

It's an obvious way to bolster Facebook's mobile efforts—a key area of worry for Facebook's new investors.

Interestingly, virtual gifts were an early idea for revenue that Facebook tried out, but ultimately abandoned. Sales of these gifts—in essence, digital icons that people could bestow on their friends as a means of congratulating (or teasing) them—amounted to about $10 million a year.

The payments system Facebook used for its virtual gifts became Facebook Credits, though, and that virtual currency, used in the social games Zynga and other companies build on Facebook's platform, is Facebook's biggest source of revenues besides advertising.